Treatment of wells with fluids containing complexes

ABSTRACT

A subterranean formation surrounding a wellbore is treated by injecting into the formation a water-based viscous fluid containing a complex produced by the reaction of an aliphatic quaternary ammonium compound with a water-soluble compound selected from the group consisting of monosaccharides, disaccharides, trisaccharides, polysaccharides, and long chain synthetic hydroxylated polymers which yield such complexes at a temperature between about 20*C and about 205*C or higher. The complexes permit the formation of emulsions and other viscous fluids which are more stable at elevated temperatures and in the presence of salts than those prepared with other materials and thus facilitate the treating of high-temperature formations not readily susceptible to treatment with other water-based fluids. Fluids containing the complexes are particularly useful as hydraulic fracturing fluids.

United States Patent 1191 Kiel [ TREATMENT OF WELLS WITH FLUIDSCONTAINING COMPLEXES Othar M. Kiel, Houston, Tex.

[73] Assignee: Esso Production Research Company,

Houston, Tex.

22 Filed: June 15, 1972 211 Appl. No.: 263,081

Related US. Application Data [63] Continuation-in-part of Ser. No.146,349, May 24, 1971, Pat. No. 3,710,865, which is acontinuation-in-part of Ser. No. 76,887, Sept. 30, 1970, abandoned.

[75] Inventor:

[52] US. Cl 166/308, 166/307, 252/8.55 R [51] Int. Cl E2lb 43/26, E2lb43/27 [58] Field of Search 166/308, 307, 305 R,

[56] References Cited UNITED STATES PATENTS 3,163,602 12/1964 Lindblomet a]. 252/8.55 3,305,016 2/1967 Lindblom et a1. 166/275 X 3,417,82012/1968 Epler et a1. 166/308 3,422,890 1/1969 Darley 166/274 3,446,7955/1969 Boudreaux et a1 252/8.55 R X 3,475,334 /1969 Boudreaux 166/308 XSept. 25, 1973 3,483,121 12/1969 Jordan 166/308 X 3,615,794 5/1968Nimerick 252/8.55 R X 3,634,237 1/1972 Crenshaw et a1. 252/8.55 R3,637,520 l/1972 Schweiger 252/316 Primary Examiner-Stephan J. NovosadAttorney-lames A. Reilly et a1.

[5 7] ABSTRACT A subterranean formation surrounding a wellbore istreated by injecting into the formation a water-based viscous fluidcontaining a complex produced by the reaction of an aliphatic quaternaryammonium compound with a water-soluble compound selected from the groupconsisting of monosaccharides, disaccharides, trisaccharides,polysaccharides, and long chain I synthetic hydroxylated polymers whichyield such complexes at a temperature between about C and about 205C orhigher. The complexes permit the formation of emulsions and otherviscous fluids which are more stable at elevated temperatures and in thepresence of salts than those prepared with other materials and thusfacilitate the treating of high-temperature formations not readilysusceptible to treatment with other waterbased fluids. Fluids containingthe complexes are particularly useful as hydraulic fracturing fluids.

Claims, 5 Drawing Figures TEMPERATURE STABILITY OF EMULSIONS VISCOSITYCENTIPOISES TEMPERATURE F VISCOSITY CENTIPOISES VISCOSITY CENTIPOISESPAIENIEIJSEF25I975 3,760,881

SIIEEI 1 III 2 TEMPERATURE STABILITY OF EMULSIONS IIO FigIl TEMPERATUREF FLUID STABILITY AT 300 F FLUID STABILITY AT 300 F 50 COMPLEX OF 2 LBSGUAR GUM/BBL AND L75 LBS/BBL OF LONG CHAIN QUATERNARY AMMONIUM CHLORIDEIN BRINE 2 LBS GUAR GUM/BBL 30 IN FRESH WATER COMPLEX OF 2 LBS GUARGUM/BBL AND L75 LBS/BBL OF LONG CHAIN QUATERNARY AMMONIUM CHLORIDE INFRESH WATER 2 LBS GUAR GUM/BBL IN BRINE VISCOSITY CENTIPOISES I l I I0TIME MINUTES Fig. 2

I 20 IO 20 TIME MINUTES Fig. 3

PAIENTEIISEPZSISTZI SHEET 2 [IF 2 STABILITY OF QUATERNARY AMMONIUMCOMPOUND-GUAR GUM COMPLEXES IN BRINE AT 200 F U) 5, QUAT AMM. COMPOUND A6 E E 30- m QUAT. AMM. COMPOUND B O 20- QUAT. AMM. COMPOUND 0 Q IO I I Il I Q 0 IO 20 30 TIME MINUTES Fig. 4

VISCOSITY CENTIPOISES STABILITY OF QUATERNARY AMMONIUM COMPOUND-GUAR GUMCOMPLEX IN OIL-BRINE SYSTEM AT 300 F I COMPLEX OF 2 LBS GUAR GUM/BBL ANDL75 LBS/BBL OF LONG CHAIN QUATERNARY AMMONIUM CHLORIDE IN BRINE WITH 5VOL.% OIL I I l 0 IO 20 30 TIME MINUTES Fig. 5

TREATMENT OF WELLS WITH FLUIDS CONTAINING COMPLEXES CROSS REFERENCE TORELATED APPLICATIONS This application is a continuation-in-part ofapplication Ser. No. 146,349, filed in the U.S. Patent Office on May 24,1971, now US. Pat. No. 3,710,865, which is a continuation-in-part ofapplication Ser. No. 76,887, filed on Sept. 30, 1970, and now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to the treatment of subterranean formations and to fluids foruse in hydraulic fracturing and other well treating operations.

2. Description of the Prior Art Hydraulic fracturing has been widelyused as a means for improving the rates at which fluids can be injectedinto or withdrawn from subterranean formations surrounding oil wells andsimilar boreholes. The methods employed normally involve the injectionof a viscous fracturing fluid having a low fluid loss value into thewell as a rate sufficient to generate a fracture in the exposedformation, the introduction of fluid containing suspended propping agentparticles into the resultant fracture, and the subsequent shutting in ofthe well until the formation is closed on the injected particles. Thisresults in the formation of high-conductivity channels through whichfluids can thereafter be injected or produced. The conductivity obtainedis a function of the fracture dimensions and the permeability of the bedof propping agent particles within the fracture.

Experience has shown that the benefits obtained from hydraulicfracturing depend to a large extent on the properties of the fluidemployed. Fluids used in the past include viscous crude oils andpetroleum fractions, aqueous liquids containing thickening agents andother additives, and emulsions of various types. Certain oilin-wateremulsions containing polymeric thickening agents in the external phasehave been recently found to be particularly effective. It has been shownthat these fluids often permit the generation of wider fractures thancan be obtained with gelled water fluids and other conventional systems,that they facilitate the transport and placement of high concentrationsof relatively large propping agents needed for the formation ofhigh-conductivity fractures, that they can be pumped into wells at therequired rates without excessive friction losses in the tubing orcasing, that the emulsion constituents can be readily removed from theformation following fracturing operations, and that such fluids havehigher efficiencies and are considerably less expensive than many of thehigh-viscosity gelled fluids that have been widely used in recent years.

One factor which has limited the use of emulsions and other water-basedfluids in hydraulic fracturing and other well treating operations hasbeen the tendency of the additives used in such fluids to lose theireffectiveness at elevated temperatures and in the presence of salts. Ithas been found that fluids prepared with conventional emulsifyingagents, thickeners, and similar materials are often unstable in thepresence of monovalent ions at temperatures of about 225F or higher andmay lack stability at even lower tempera- -tures if divalent ions arepresent in significant quantities. This has limited the use of oilfieldbrines for the SUMMARY OF THE INVENTION The present invention relates toimproved well treating operations carried out with water-based fluidswhich have better stability than those available in the past. Inaccordance with the invention, it has now been found that aliphaticquaternary ammonium compounds can be reacted with water-solublecompounds selected from the group consisting of monosaccharides,disaccharides, trisaccharides, polysaccharides, and long chain synthetichydroxylated polymers which will complex with the quaternary ammoniumcompounds, at temperatures between about 20C and about 205C or higher,to form complexes which can be used in turn to produce gels, emulsionsand other water-based fluids that are surprisingly stable at elevatedtemperatures and in the presence of salts. Laboratory work and fieldtests have shown that these complexes permit the preparation of fluidswhich are suitable for use in well treating operations from water orbrine and a variety of different hydrocarbon liquids, that such fluidshave sufficient stability to permit their use in high-temperature wellswhere fluids employed in the past are often inadequate, and that suchfluids have rheological properties and other characteristics which makethem particularly effective in hydraulic fracturing and similar welltreating operations. The injection of such a fluid into a subsurfaceformation surrounding a well at fracturing rates often results in thegeneration of a fracture with greater dynamic width and length than canbe obtained with a conventional fluid under comparable conditions andfrequently permits the treatment of formations that have been difficultor impossible to treat with fluids available in the past.

Experience has shown that complexes prepared by the reaction of longchain quaternary ammonium halides useful as cationic emulsifying agentswith high molecular weight water-soluble polysaccharides such as guargum or a similar galactomannan are particularly effective for purposesof the invention. The addition of naphtha, liquefied petroleum gases,kerosene, diesel oil or a similar low-viscosity hydrocarbon liquid towater or brine containing such a complex normally results in theformation of an oil-in-water emulsion which is quite stable attemperatures of 300F and higher and is rela-' tively unaffected by thepresence of calcium and other divalent ions. These emulsions have madepossible the fracturing of wells that are difficult at best to fracturewith conventional fluids and have reduced the cost of treating suchwells substantially.

BRIEF DESCRIPTION OF THE DRAWING FIG. I in the drawing is a plot ofviscosity vs. temperature for various fluids which shows the superiorityof the fluids used in accordance with the invention over other fluids;and

FIGS. 2 through 5 are plots of viscosity vs. time for various fluidsystems which further demonstrate the improved characteristic of thefluids employed for purposes of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The improved well treatingfluids employed for purposes of the invention are prepared withcomplexes formed by the reaction of aliphatic quaternary ammoniumcompounds with water-soluble compounds selected from the groupconsisting of monosaccharides, disaccharides, trisaccharides,polysaccharides, and long chain synthetic hydroxylated polymers whichyield such complexes, under the conditions of the system, attemperatures in the range between about 20C and about 205C or higher. Avariety of different quaternary ammonium compounds having alkyl, alkenylor alkaryl substituents containing from about one to about 24 carbonatoms per substituent may be employed. These are preferably used in theform of the quaternary ammonium halides but in some cases hydroxides,sulfates, sulfonates and other derivatives may also be employed.Representative quaternary ammonium compounds that may be reacted withthe water-soluble compounds include tetramethyl ammonium hydroxide,tetraethyl ammonium chloride, tetrapropyl ammonium chloride, tetrabutylammonium bromide, tripropyl methyl ammonium sulfate, dimethyl dihexylammonium chloride, diethyl dibutenyl ammonium chloride, dibutyldioctadecyl ammonium chloride, trimethyl benzyl hydroxide, hexyltrioleylammonium hydroxide, dibenzyl dihexadecyl ammonium sulfonate, trimethylcyclohexyl ammonium chloride, didodecyl dicyclopentyl ammonium chloride,trimethyl eicosyl ammonium chloride, and the like. The quaternaryammonium compounds containing from about 16 to about 48 carbon atoms permolecule are generally preferred.

Also useful for purposes of the invention are quaternary ammoniumcompounds containing substituent groups derived from naturally-occurringmaterials such as coconut oil, tallow, soybean oil and the like. Suchcompounds normally contain from 1 to 3 methyl groups and l or more longchain aliphatic substituent groups. One example of such a substituentgroup is the coco group derived from coconut oil. This group consists oflong chain aliphatic radicals containing from about to about 18 carbonatoms. A typical analysis shows about 4.0 percent C radicals, about 55.5per cent C radicals, about 14.0 percent C radicals, and about 4.0percent C radicals. The tallow group normally consists primarily ofsaturated and unsaturated C and C radicals; while the soya group is madeup of saturated and unsaturated C to C radicals in somewhat differentproportions. Representative of the quaternary ammonium compoundscontaining mixed substituent groups are trimethyl tallow ammoniumhydroxide, dimethyl dicoco ammonium chloride, dimethyl soyzbenzylammonium chloride, diethyl tallow hexyl ammonium sulphate, methyltrisoya ammonium hydroxide and the like.

A particularly effective class of long chain quaternary ammoniumconpounds useful for purposes of the invention is made up of the longchain quaternary ammonium halides prepared by the alkylation of primaryamines having aliphatic groups of from about eight to about 20 carbonatoms in length, secondary amines containing C to about C aliphaticsubstituents, and polymeric fatty acid amines having aliphaticsubstituents up to about eight carbon atoms in length with methylchloride or the like in a low-boiling alcohol or similar solventcontaining a base such as sodium hydroxide or a mixture of sodiumhydroxide and sodium bicarbonate. Quaternary ammonium halides producedin this manner are marketed commercially for use as cationicemulsifiers. Such materials can be obtained in various grades, dependingon the lengths of the aliphatic substituent groups, the percent activeingredients present, the solvent employed, and other factors. Theygenerally have hydrophilic-lipophilic balance values between about 8 andabout 18. Among the cationic emulsifiers found especially useful forpurposes of the invention are the water-soluble tallow-based quaternaryammonium chlorides available from Enjay Chemical Company, Houston,Texas, under the designation Corexit 8596. The asphalt emulsifier soldby Armour Industrial Chemical Company, Chicago, Illinois, under thetradename Redicote E-l l is also useful. Other cationic emulsifiersinclude the alkyl ammonium halides in which one alkyl group containsfrom about six to about 18 carbon atoms and the other substituentsattached to the nitrogen atom or hydrogen atoms are alkyl groups of fromone to four carbon atoms in length. It will be understood, of course,that all long chain quaternary ammonium compounds are not equallyeffective for purposes of the invention and that some will thereforenormally give better results than others.

The water-soluble compounds with which the quaternary ammonium compoundsare reacted to form the complexes employed for purposes of the inventionare selected from the group consisting of monosaccharides,disaccharides, trisaccharides, polysaccharides, and long chain synthetichydroxylated polymers which yield complexes under the conditions of thesystem. It has been shown that quaternary ammonium compounds are capableof reacting with a wide variety of different water-soluble materialscontaining anionic exchange groups or radicals to which the cationicportion of the quaternary ammonium compounds may attach. These groupsinclude primary hydroxyl groups, secondary hydroxyl groups, carboxylgroups, carbonyl groups and the like. Representative examples ofmaterials containing such groups of radicals that may be employed forpurposes of the invention include monosaccharides, disaccharides, andtrisaccharides such as glucose, mannose, galactose, fructose, arabinose,lactose, sucrose, rafi'mose, and the like. Also suitable arewater-soluble polysaccharides of vegetable, animal or microbial origin,including both the structural and nutrient types. Examples of thesematerials include suitable derivatives of vegetable nutrientpolysaccharides such as starches and inuline, amylose and amylopectinfor example; derivatives of vegetable structural polysaccharides such ascelluloses, xylans, pectins, algins, and galactomannans; natural gumssuch as gum karaya, gum tragacanth, and the like; animal polysaccharidessuch as glycogens, chitins, and mucopolysaccharides; and microbialpolysaccharides such as levans, dextrans, the polysaccharides producedby bacteria of the genus Xanthomonas; and polymers produced by moldssuch as Sclerotium Glucanicum, Corticium Rolfsii and the like. Othermaterials that can be used include long chain synthetic polymerscontaining hydroxyl groups and other radicals through which thequaternary ammonium compounds can be formed. Examples of these includethe partially hydrolyzed polyacrylamides, polyvinylalcohols, polyvinylcarboxylic acids neutralized with amines and bases, polyacrylic acids,and the like. Mixtures of these and similar materials can also be used.Some of these materials, of course, are presenty too expensive for useon a routine basis. The preferred materials, both from the standpoint ofperformance and cost, include the readily available water-solublepolysaccharides and polysaccharide derivatives such as guar gum,carboxylmethylcellulose, hydroxyethylcellulose, andcarboxymethylhydroxyethylcellulose. Guar gum has been found to beparticularly effective for purposes of the invention.

The reaction of the quaternary ammonium compounds with the water-solublehydroxy compounds to produce the complexes employed for purposes of theinvention may be carried out in either aqueous or oleaginous media. Ifan aqueous medium is employed, it is normally preferred to first add thequaternary ammonium compound to water or brine in a concentrationbetween about 0.00l and about 5 percent by weight. The polysaccharide orother water-soluble compound is then added in a concentration betweenabout 0.001 and about 5 percent by weight and the solution is agitatedto promote uniform dispersion of the materials in the solution. Reactionof the materials to form the complex normally occurs rapidly. Dependingupon the particular reactant selected and the conditions employed, itmay be accompanied by an increase in the viscosity of the solution orprecipitation of the complex. Experience has shown that complexing ofthe quaternary ammonium compounds with high molecular weightwatersoluble polymers often results in a formation of a product whichdoes not have sufficient hydrophilic groups to render it soluble infresh water but that such materials can generally be solublized inbrine. Brines are generally employed for the preparation of water-basefluids to be used in hydraulic fracturing and other well treatingoperations because of the deleterious effect of fresh water on manysubterranean formations. The fact that the complexes obtained withcertain starting materials may not be soluble in fresh water istherefore not a serious drawback.

The process described above is generally used for the preparation ofwater-based fluids that are to be used in hydraulic fracturing and otherwell treating operations. By preparing the complex in the water or brineto be employed in the field, the necessity for recovering and handlingthe complex can be avoided. If desired, however, the soluble complexescan be precipitated from aqueous media in which they are prepared byadding methanol, ethanol, or a similar low molecular weight alcohol tothe media. The precipitates thus obtained, as well as precipitates whichare formed naturally on reaction of the starting materials, can berecovered by decanting, filtration or centrifugation. These can then bewashed with alcohol or the like to remove any unreacted materials thatmay be present, dried at low temperature, and packaged for later use.

If an oleaginous medium is employed for preparation of the complex, thepolysaccharide or other hydroxy compound is first dispersed in kerosene,a light mineral oil or a similar fluid. The quaternary ammonium compoundis then added and the reaction medium is stirred to promote effectivecontact between the two reactants. The concentrations in which the twomaterials are employed may be varied considerably but it is normallypreferred to use the materials in approximately equal quantities byweight. The reaction can generally be accelerated by heating the oil.The occurrence of the reaction is generally accompanied by a change inthe appearance of the materials and the formation in the bottom of thereaction vessel of the particulate solid which is readily identifiable.The reaction in oil or a similar medium normally takes place over aperiod ranging from a few minutes to an hour or more, depending upon theparticular reactants selected. The complex formed can be recovered fromthe reaction mixture by decanting, filtration, or centrifugation, washedwith alcohol or a solvent to remove the remaining oil, and then driedand packaged. In some cases, it may be desirable to crush the productparticles to a fine powder to facilitate later use in a water-basedfluid but this step is not always necessary.

Depending upon the particular starting materials selected, the complexesprepared as described above may be employed for thickening aqueousfluids to be used in hydraulic fracturing and other well treatingoperations or used for the formation of emulsions to be employed in suchoperations. It has been found that the complexing of guar gum andsimilar polymers useful as thickening agents with the quaternaryammonium compounds improves the heat stability and thickeningeffectiveness of such polymers and in some cases may also reduceadsorption on subterranean formations. Similarly, the complexing ofquaternary ammonium compounds useful as emulsifying agents with thewatersoluble compounds generally results in a significant improvement inthe performance of the emulsifiers at high temperatures and in thepresence of divalent salts. By properly selecting the startingmaterials, it is thus possible to prepare a variety of differentcomplexes which are particularly suited for use in various types ofoilfield stimulation operations.

The complexing of guar gum and similar high molecular weightwater-soluble polysaccharides with long chain quaternary ammoniumcompounds which have hydrophilic-lipophilic balance values between about8 and about 18 results in a particularly useful class of materials thatmay be employed both as thickening agents in fluids substantially freeof oil and as emulsifiers in oil-water systems. Experience has shownthat these complexes have excellent stability at elevated temperaturesand in the presence of calcium and other divalent salts and that theycan therefore be used for the preparation of viscous solutions andemulsions having properties superior to those of many of the fluidsemployed in the past.

Water-based fracturing fluids and other well treating agents containingthe complexes prepared as described above can be prepared withoutspecial equipment. If the complex has been formulated in an aqueousmedium and not precipitated, other constituents required for the desiredwater-based fluid can simply be added in the necessary concentrations.These constituents may include acids, corrosion inhibitors, fluid losscontrol agent's, wetting agents, diverting agents, and other additivescommonly used in acidizing and acid fracturing fluids; oils, fluid losscontrol agents, propping agents, salts, gel breakers, friction reducers,and other materials frequently used in hydraulic fracturing operations;and other conventional additives that may be useful in workover fluids,completion fluids, and similar oilfield formulations. Stableoil-in-water emulsions containing the complexes can be readily preparedby adding naphtha, liquefied petroleum gases, kerosene,

diesel oil, lease crude oil, or a similar hydrocarbon liquid ofrelatively low viscosity to the water or brine containing the complexand agitating the fluid, either by means of mixers or similar devices orby circulating it through a pump or blender. If a dried complex is used,similar procedures can be employed after the dried material has beensolublized in water in the necessary concentration.

The procedures to be employed in well stimulation operations carried outwith fluids containing the complexes will depend upon the particulartype of operation contemplated. In acidizing operations where thecomplexes are to be employed for thickening an aqueous fluid which is tobe injected into the formation in advance of the acid, for example, thisaqueous fluid is normally prepared by adding the quaternary ammoniumcompound and polysaccharide or similar material to brine inapproximately equal concentration of from about 2 to about 4 pounds perbarrel and allowing the additives to react as described above. Theresulting viscous solution is then injected into the well under a pressure sufficient to part the exposed formation. After the viscous fluidhas been injected and a fracture extending away from the wellbore hasbeen formed, a solution of hydrochloric acid or the like is introducedinto'the fracture containing the viscous fluid. The injected acidchannels through the viscous solution within the fracture so that littlereaction of the acid with the surrounding carbonate formation takesplace until the acid reaches the outer ends of the fracture. Thispermits the transport of unreacted acid over much greater distances thancan normally be obtained in ordinary acidizing operations. The injectedacid may be followed with a brine afterflush to displace it away fromthe wellbore. After injection of the acid and afterflush have beencompleted, the well may be shut in overnight and then placed onproduction. The increase in permeability obtained as a result of thereaction of the acid with the formation normally results in asignificant increase in the production rate.

In hydraulic fracturing operations in which the complexes are used forthe formation of stable emulsion fracturing fluids, a brine preflushcontaining'fluid loss agents will normally first be injected to breakdown the formation. An emulsion prepared from field brine and kerosene,lease condensate or other oil is then generally employed. This emulsionis normally produced by adding guar gum or a similar water-solublepolymer and a quaternary ammonium chloride cationic emulsifier orsimilar compound to the brine. The brine containing these materials andthe oil are mixed to form the emulsion as the fluids are pumped throughthe blender and into the well. A fluid loss agent may be incorporatedinto the initial portion of the emulsion which is injected as a pad andserves to extend the fracture. After the pad has been injected, theintroduction of sand or other propping agent particles into the fluid inthe blender is commenced. The sand concentration is normally increasedstep-wise up to about 4 pounds or more per gallon. After the requiredvolume of emulsion containing the propping agent has been put away, thewellbore may be flushed with kerosene, lease condensate or other fluidand the well shut in. The emulsion thus injected into the formationgradually breaks during the shut in period. Thereafter, the well can beopened and returned to production. The constituents employed to form theemulsion are readily produced back into the wellbore and hence thecleanup time is normally very short. The flow rate during the cleanupperiod is generally somewhat higher than the production rate prior totreatment of the well and usually increases substantially as theemulsion constituents are displaced by the formation fluids.

Hydraulic fracturing operations in which the complexes are used asthickening agents in oil-free fluid systems, acid fracturing operationswherein the complexes are employed to stabilize oil-acid emulsions,acidizing operations in which the complexes serve to build viscosity inthe acidizing solutions, and other well treating operations may becarried out by using procedures generally similar to those describedabove. As indicated earlier, the precise steps to be employed in suchoperations will depend in part on the nature of the particular operationto be carried out and need not be described in detail to permit anunderstanding of the invention.

The invention can be further illustrated by considering the results oflaboratory tests carried out with complexes prepared from variousquaternary ammonium compounds and water-soluble polysaccharides andrelated materials and field tests of oilfield stimulation processesusing such complexes in aqueous solutions and emulsions.

EXAMPLE I In a first series of laboratory tests, complexes were preparedby reacting approximately equal parts by weight of a commercial longchain quaternary ammonium chloride, marketed by Armour IndustrialChemical Company. Chicago, Illinois, under the tradename Redicote El 1for use as a cationic asphalt emulsifying agent, with variouspolysaccharides and other related materials in an oil environment. Thereactions were carried out by adding the starting materials to samplesof a light mineral oil and then heating the samples to a temperature ofabout 200F while providing agitation. As the complexes formed, theyaccumulated at the bottoms of the beakers as light yellow granularmaterials which were quite different in appearance from the startingmaterials added to the oil. The reaction times ranged from a few minutesto about 30 minutes. The reaction products thus obtained were recoveredby decanting the oil, washed, and then tested to determine whether theywould build viscosity in fresh water, a synthetic 10 pounds per gallonoilfield brine, and dilute hydrochloric acid. The polysaccharides andrelated materials employed and the results of the solubility tests withthe resulting complexes are shown in the table set forth below.

TABLE I Reaction of Polysaccharides and Related Materials withQuaternary Ammonium Chloride Complex Built Viscosity in Polyacrylamidemarketed as a thickening agent in oilfield operations Commercial starchSugar (sucrose) Polysaccharide produced by Xanthomonas Campesm's,marketed for use in oilfield drilling muds No complex recovered Nocomplex recovered Soluble but little effect upon viscosity No complexrecovered it can be seen from the results set forth in the above wasfound that the guar gum readily reacted h the table that the guar gum,hydroxyethyl cellulose, and suquaternary ammonium compound in fresh erto Grow reatii]y reacteti with the quaternary ammonium form a solublecomplex that gave a substantial increase chloride to f compiexes Theother matei-ia]S either in vlscosity over that obtained with the guargum alone. did not form complexes under the particular conditionsHydroxyethyt cellulose the P y y and the employed f d complexes ininsufficient quanti polysaccharide produced by Xanthomonas Campestristies to permit their recovery The reaction products all reacted with thequaternary ammonium chloride to tained with the guai. gum andhydioxyethyi cellulose form precipitates. As indicated earlier, testshave were soluble in fresh water, brine and hydrochloric Show" that Suchprecipitates are useful as thickening acid and appeared to be excellentviscosity builders. agents in fluids Prepared from Oilfield brineso ghSuch materials may be employed as thickening agents all of the testsdescribed up to this point were carried in a variety of aqueous fluidsemployed in oilfield well out with the Same quaternary ammoniumchlfll'ide, it treating operations. The complex obtained with suhas beenfound that similar reactions occur with other crose, on the other hand,was soluble in the fresh water, water-soluble quaternary ammoniumcompounds. Albrine and acid but in the concentrations used had verythough the exact mechanisms involved are not fully unlittle effect uponthe viscosities of the fluids. Other tests derstood, it has beensuggested that the chlorides and with this material showed that it hadgood emulsifying similar compounds are first hydrolyzed to form thecorproperties and permitted the formation of more stable respondinghydroxides and that these then react with oil-in-water emulsions thanwere obtained with the the polysaccharides and related materials.Regardless quaternary ammonium chloride alone. Although comof themechanism, the results obtained demonstrate plexes were not recoveredfrom the oil samples in that the complexes can be formed with a varietyof difwhich the polyacrylamide, and the bacterial polysacferent startingmaterials having diverse physical and charide produced by XanthomonasCampestris were chemical properties. used, later tests indicate thatreaction products formed with these materials can be recovered asprecipitates EXAMPLE lV under somewhat different reaction conditions.

' In still another series of experiments, oil-in-water EXAMPLE uemulsions were prepared using a complex of the type Following the testsdescribed above, a second series employed for purposes of the inventionand various of experiments in which the quaternary ammonium combinationsof emulsifying agents and polymers chloride referred to above wasreacted with guar gum, which do not react to form such complexes. Thesamhydroxyethyl cellulose, polyacrylamide, and the polyples tested wereprepared by first adding the polymers saccharide produced by XanthomonasCampestris were to water or brine in the required concentrations andalcarried out in brine. In each case the polymer was lowing them tohydrate, introducing the emulsifying added to a sample of the brine andallowed to hydrate. agents, mixing the resulting solutions with samplesof The qauternary ammonium chloride was then added in kerosene in aratio of 2 parts of oil to 1 part of aqueous approximately the sameconcentration by weight and solution, and then agitating the mixtures toproduce the the sample was agitated to promote intimate mixing ofemulsions. The materials employed in each of the test the reactantmaterials. All four of the polymers readily emulsions are shown in thetable set forth below.

TABLE II Compositions of Oil-In-Water Emulsions 1 Emulsion No.Emulsil'ylng agent Polymer Other constituents 1 1.75 lhjhbl. commercialnonionic emulsifier 2.011).!hhl. guar gum 7 lhJhhl. KCl. 2 1.0 lb./bl)l.commercial anionic emulsifier 0.5 lb.(/lhhl. guar gum, 1.0 lb./bbl.polyaeryl- 7 lb./bbl. KCl, 0.1 1b./bb1 F so pH adj,

ami e. to 8. 3 1.75 ll). 'bl)l. long chain quaternary nmmo- 2.5'lb./hbl.guar gum Brine, 7 ll)./bl l. KCl, 0.1 lb./bbl. F930,,

nium chloride. pII adj. to 8, 4 2.1 lbJbbl. long chain quaternary ammo0.5 llx/bbl. guar gum, 1.0 lbJbbl. hydroxy- 7 lbJbbl. KCl, 0.11b./bb1. Fso nium chloride. ethylcellulosc. 5 2.4ll)./bbl. commercial uoniouicemulsifier 0.5 lbJbbl. zu-ar gum, 1.5 lb./bl)l. hydroxy- 7 lb./bl l.K01, 0.1 ll)./bbl. FeSO pH adj.

ethyleellulose. to 8.

l All fluids were prepared with 2 volumes of kerosene and 1 volume ofAYlipzhl (JD-128, marketed by GAF Corporation, New York, water. few or.\'aleo AP-iOl, marketed by Nalco Chemical Company, Chicago, 4 RedicoteE-ll, marketed by Armour Industrial Chemical Com- Illinois. pany,Chicago, Illinois.

reacted with the quaternary ammonium chloride to Samples of each of theemulsions prepared as deform smooth, clear solutions having higherviscosities scribed above were then tested at various temperatures thanthe brine samples containing the polymers alone. in a temperature bathwith a Model 50B Fann Viscom- A subsequent test with the complex formedwith the eter. The viscosity of each emulsion was measured atpolysaccharide produced by Xanthomonas Campestris temperatures betweenl50F and 350F and plotted aas showed that this complex could be readilyprecipitated shown in FIG. 1 of the drawing. It can be seen from the bythe addition of methanol or a similar low molecular FIGURE that Emulsion3 was markedly superior to the weight alcohol and resolublized in freshwater to proother fluids. This composition, prepared by reacting duce aviscous fluid. This provides a convenient means guar gum and a longchain quaternary ammonium chlofor handling and storing the complex. ridemarketed as a cationic asphalt emulsifier to form EXAMPLE m a complexand then adding kerosene to produce the emulsion, had a viscosity ofabout centipoises at Still another series of laboratory experimentssimilar 250F and about 50 centipoises at 350F. The next best to thosedescribed above was carried out using fresh material was Emulsion 4,which contained a complex water in place of the brine or oil employedearlier. It of the same quaternary ammonium chloride with a mixture ofguar gum and hydroxyethylcellulose in a lower concentration. Althoughthis fluid underwent a rapid loss in viscosity as the temperature wasincreased'from 150F to about 250F, the viscosity remained relativelyconstant between about 250F and 350F. The remaining fluids were preparedwith emulsifiers which do not react with the long chain polysaccharidesto form complexes and had essentially no viscosity at temperatures of350F. These data demonstrate the superior high temperature properties ofthe fluids employed for purposes of the invention and show that thecomplexes permit the preparation of emulsions which are relativelystable at temperatures of 350F and higher.

EXAMPLE V To To further demonstrate the superior thickening powers ofthe materials employed for purposes of the invention, samples of acommercial guar gum marketed for use in oilfield operations and acomplex of this same material with a long chain coconut oil basedquaternary ammonium chloride emulsifier available from Enjay ChemicalCompany, Houston, Texas, as Surfactant 8549" were prepared. The guar gumwas added to a sample of a synthetic brine having a density of poundsper gallon in a concentration of 2 pounds per barrel. The complex wasprepared by adding guar gum to a separate brine sample in the sameconcentration and then reacting this with 1.75 pounds per barrel of thelong chain quaternary ammonium chloride. The two samples were thentested with a Model 508 Fann Viscometer in a temperature bath maintainedat 300F for a period of about 30 minutes. The sample containing only theguar gum lost viscosity rapidly during the first 5 minutes and at theend of the 30 minute period had a viscosity of only about 7 centipoises.The sample containing the complex of guar gum and the long chainquaternary ammonium chloride also showed a rapid viscosity lossinitially but at the end of about 30 minutes still had a viscosity ofabout 17 centipoises. This is shown in FIG. 2 in the drawing. These datademonstrate that formation of the complexes improves the heat stabilityof polymeric thickening agents and thus permits the use of guar gum andsimilar water-soluble polysaccharides as thickeners in brines at highertemperatures than might otherwise be feasible.

EXAMPLE VI FIG. 3 in the drawing illustrates the results of a test infresh water similar to that shown for a brine system in FIG. 2. It canbe seen that the guar gum sample lost essentially all of its viscosityafter about 27 minutes at a temperature of 300F and that the samplecontaining the complex of guar gum and the long chain quaternaryammonium chloride still had a viscosity of about 7 centipoises afterabout 25 minutes at 300F. Although both samples were less stable infresh water than in the brine used to obtain the data of FIG. 2, thesample containing the complex was again significantly better than thatcontaining the guar gum alone.

EXAMPLE VII A further series of tests similar to those of FIGS. 2 and 3was carried out with complexes prepared from three different quaternaryammonium compounds. The results bf these tests are shown in FIG. 4 ofthe drawing. Quaternary ammonium compound A was a cationic emulsifieravailable from Enjay Chemical Company,

Houston Texas, under the tradename Enjay LD- 29108; quaternary ammoniumcompound B was a cationic asphalt emulsifier marketed under thetradename Redicote E-S by Armour Industrial Chemical Company, Chicago,Illinois; and quaternary ammonium compound C was a similar cationicasphalt emulsifier marketed by Armour Industrial Chemical Company underthe tradename Redicote E-l 1. In each case the guar gum was used in aconcentration of 2 pounds per barrel and the cationic emulsifier wasemployed in a concentration of 1.75 pounds per barrel. None of thesystems contained any oil. It can be seen from FIG. 4 that all threequaternary ammonium compounds gave relatively high viscosities at the200F test temperature and that the formation of the complexes improvedthe performance of the guar gum in brine. The data also show that allquaternary ammonium compounds are not equally effective for purposes ofthe invention and that certain materials will therefore be preferred.

EXAMPLE VIII FIG. 5 in the drawing shows the results of still anothertest in which 2 pounds per barrel of guar gum was complexed with 1.75pounds per barrel of a long chain quaternary ammonium chloride, EnjayLD-29l08, in brine and 5 percent oil by volume was added to the system.The viscosity of the resulting fluid was measured at 300F during a 30minute test period. The data show that the system had good stability,even though the presence of the oil may have caused some loss inviscosity. The complexes employed for purposes of the invention thuspermit the formulation of a variety of different fluids useful inoilfield well treating operations.

EXAMPLE IX Following the tests described above and other laboratorywork, a hydraulic fracturing field test was carried out using a complexof guar gum and a long chain quaternary ammonium chloride marketed byEnjay Chemical Company of Houston, Texas, as a cationic emulsifier underthe tradename Corexit 8596". The well in which the field test wascarried out was a deep gas well in South Texas which did not have enoughpressure to produce into the sales line. Analysis of the well indicatedthat a substantial increase in production could probably be obtained ifan effective hydraulic fracturing operation could be carried out. Afracturing operation which called for the injection of about 58,000pounds of 20-40 mesh sand in an oil-in-water emulsion prepared fromfield brine and lease condensate was designed.

The emulsion fracturing fluid to be used in the test was prepared withthree SOD-barrel tanks. One of these tanks was filled with field brinecontaining from 30 to 40,000 parts per million of sodium chloride. Theother tanks were filled with lease condensate. Ten gallons of ammoniumhydroxide was added to each of the condensate tanks to neutralize anyacids present. One thousand pounds of guar gum and two 55-gallon drumsof Corexit 8596 were added to the brine to give a guar gum concentrationof 2 pounds per barrel and a quaternary ammonium chloride concentrationof about 1.75 pounds per barrel. The brine containing the guar gum andquaternary ammonium chloride was then circulated through the blender andback into the tank until the constituents had been thoroughly mixed anda complex of the guar gum and quaternary ammonium compound had beenformed in the brine. No difficulties in forming the complex wereencountered.

Following preparation of the brine solution containing the complex asdescribed above, the fracturing operation was commenced by injectinginto the well at fracturing rates 250 barrels of salt water containing acommercial fluid loss agent in a concentration of 20 pounds per 1,000gallons. The pressure increased rapidly and then dropped off as thisfluid was injected, indicating that the formation had been broken downand that a fracture had been initiated. Once this had been accomplished,preparation and injection of the emulsion were started. The brinecontaining the guar gumquaternary ammonium chloride complex and thelease condensate were pumped into the blender from the brine andcondensate tanks, mixed continuously, and injected into the well as asmooth, tight emulsion. A fluid loss agent composed of equal parts of acommercial fluid loss material and silica flour were added to the systemat the blender in a concentration of 20 pounds per barrel. Injection ofthe emulsion containing the fluid loss agent was continued until a padof 36,000 gallons had been injected to extend the fracture to thedesired dimensions. The introduction of sand at the blender was thenstarted. Simultaneously, the concentration of the fluid loss agent wasreduced to a level of pounds per gallon. The concentration of the sandused as the propping agent was increased from 1 pound per gallon toabout 4 pounds per gallon during injection of the first 4,000 gallons ofsand-containing emulsion. A total of 22,000 gallons of emulsioncontaining a total of 58,000 pounds of sand was injected into the welland lease condensate was then used to flush down the wellbore and theperforations. After this had been done, the well was shut in and letstand overnight.

On opening the well to restore production following the shut-in period,gas was initially produced at the rate of about 800,000 cubic feet perday. During the first six hours of production, 600 barrels of water andlease condensate were produced. The gas production rate continued toincrease as the well cleaned up and leveled out at about 1.2 millioncubic feet per day.

I claim:

1. A method for the treatment of a subterranean formation surrounding awellbore which comprises injecting into said formation a fluidcontaining a complex prepared by the reaction of an aliphatic quaternaryammonium compound with a water-soluble compound selected from the groupconsisting of monosaccharides, disaccharides, trisaccharides,polysaccharides, and long chain synthetic hydroxylated polymers whichyield such complexes at temperatures between about C and about 205C andthereafter producing fluids from said formation into said wellbore.

2. A method as defined by claim 1 wherein said water-soluble compound isa galactomannan.

3. A method as defined by claim 1 wherein said water-soluble compound issucrose.

4. A method as defined by claim 1 wherein said watersoluble compound isa polysaccharide.

5. A method as defined by claim ll wherein said water-soluble compoundis hydroxyethylcellulose.

6. A method as defined by claim 1 wherein said water-soluble compound isa polysaccharide produced by bacteria of the genus Xanthomonas.

7. A method as defined by claim ll wherein said quaternary ammoniumcompound is a quaternary ammonium chloride.

8. A method as defined by claim ll wherein said quaternary ammoniumcompound contains from about 16 to about 48 carbon atoms per molecule.

9. A method as defined by claim ll wherein said quaternary ammoniumcompound contains from 1 to 3 methyl groups and at least one long chainaliphatic group.

10. A method as defined by claim 1 wherein said quaternary ammoniumcompound is a cationic emulsifier having a hydrophilic-lipophilicbalance value between about 8 and about 18.

l l. A method for the hydraulic fracturing of a subterranean formationsurrounding a wellbore which comprises injecting into said formation atfracturing rates a viscous fluid containing a complex produced by thereaction of an aliphatic quaternary ammonium compound and awater-soluble polysaccharide and thereafter producing fluids from saidformation into said wellbore.

12. A method as defined by claim 11 wherein said viscous fluid is anoil-in-water emulsion.

13. A method as defined by claim 111 wherein said viscous fluid is anemulsion containing oil as the internal phase and an acid as theexternal phase.

14. A method as defined by claim llll wherein said quaternary ammoniumcompound is a cationic emulsifier and said polysaccharide is guar gurn.

115. A method as defined by claim 1 ll wherein an acid solution isinjected into said formation behind said viscous fluid prior toproducing fluids from said formation.

16. A method for the hydraulic fracturing of a subterranean formationsurrounding a wellbore which comprises reacting an aliphatic quaternaryammonium compound and a water-soluble polysaccharide in an aqueousmedium to produce a complex, injecting said medium containing saidcomplex into said formation at a rate sufficient to open a fracture inthe formation, and thereafter producing fluids from said formation intosaid wellbore.

ll7. A method as defined by claim 16 wherein said quaternary ammoniumcompound is a quaternary ammonium chloride and said polysaccharide is aguar gum.

18. A method as defined by claim 16 wherein an oil is added to saidaqueous medium prior to injecting said medium.

119. A method as defined by claim 18 wherein said oil is added as saidmedium is pumped into the well.

20. A method as defined by claim 18 wherein about two volumes of oil areadded for each volume of said aqueous medium.

21. A method for the treatment of a subterranean formation surrounding awellbore which comprises reacting an aliphatic quaternary ammoniumcompound and guar gum to produce a complex, injecting an aqueous mediumcontaining said complex into said formation through said wellbore, andthereafter producing fluids from said formation into said wellbore.

22. A method as defined by claim 21 wherein said quaternary ammoniumcompound is a quaternary ammonium chloride containing tallow groups.

23. A method as defined by claim 21 wherein said aqueous medium is anoil-internal emulsion.

24. A method as defined by claim 21 wherein said aqueous medium isinjected at fracturing pressure.

25. A method as defined in claim 21 wherein said quaternary ammoniumcompound is a quaternary ammonium chloride containing coco groups.

2. A method as defined by claim 1 wherein said water-soluble compound isa galactomannan.
 3. A method as defined by claim 1 wherein saidwater-soluble compound is sucrose.
 4. A method as defined by claim 1wherein said water-soluble compound is a polysaccharide.
 5. A method asdefined by claim 1 wherein said water-soluble compound ishydroxyethylcellulose.
 6. A method as defined by claim 1 wherein saidwater-soluble compound is a polysaccharide produced by bacteria of thegenus Xanthomonas.
 7. A method as defined by claim 1 wherein saidquaternary ammonium compound is a quaternary ammonium chloride.
 8. Amethod as defined by claim 1 wherein said quaternary ammonium compoundcontains from about 16 to about 48 carbon atoms per molecule.
 9. Amethod as defined by claim 1 wherein said quaternary ammonium compoundcontains from 1 to 3 methyl groups and at least one long chain aliphaticgroup.
 10. A method as defined by claim 1 wherein said quaternaryammonium compound is a cationic emulsifier having ahydrophilic-lipophilic balance value between about 8 and about
 18. 11. Amethod for the hydraulic fracturing of a subterranean formationsurrounding a wellbore which comprises injecting into said formation atfracturing rates a viscous fluid containing a complex produced by thereaction of an aliphatic quaternary ammonium compound and awater-soluble polysaccharide and thereafter producing fluids from saidformation into said wellbore.
 12. A method as defined by claim 11wherein said viscous fluid is an oil-in-water emulsion.
 13. A method asdefined by claim 11 wherein said viscous fluid is an emulsion containingoil as the internal phase and an acid as the external phase.
 14. Amethod as defined by claim 11 wherein said quaternary ammonium compoundis a cationic emulsifier and said polysaccharide is guar gum.
 15. Amethod as defined by claim 11 wherein an acid solution is injected intosaid formation behind said viscous fluid prior to producing fluids fromsaid formation.
 16. A method for the hydraulic fracturing of asubterranean formation surrounding a wellbore which comprises reactingan aliphatic quaternary ammonium compound and a water-solublepolysaccharide in an aqueous medium to produce a complex, injecting saidmedium containing said complex into said formation at a rate sufficientto open a fracture in the formation, and thereafter producing fluidsfrom said formation into said wellbore.
 17. A method as defined by claim16 wherein said quaternary ammonium compound is a quaternary ammoniumchloride and said polysaccharide is a guar gum.
 18. A method as definedby claim 16 wherein an oil is added to said aqueous medium prior toinjecting said medium.
 19. A method as defined by claim 18 wherein saidoil is added as said medium is pumped into the well.
 20. A method asdefined by claim 18 wherein about two volumes of oil are added for eachvolume of said aqueous medium.
 21. A method for the treatment of asubterranean formation surrounding a wellbore which comprises reactingan aliphatic quaternary ammonium compound and guar gum to produce acomplex, injecting an aqueous medium containing said complex into saidformation through said wellbore, and thereafter producing fluids fromsaid formation into said wellbore.
 22. A method as defined by claim 21wherein said quaternary ammonium compound is a quaternary ammoniumchloride containing tallow groups.
 23. A method as defined by claim 21wherein said aqueous medium is an oil-internal emulsion.
 24. A method asdefined by claim 21 wherein said aqueous medium is injected atfracturing pressure.
 25. A method as defined in claim 21 wherein saidquaternary ammonium compound is a quaternary ammonium chloridecontaining coco groups.